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 * Copyright (c) 2005, 2006, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package javax.tools;

import java.io.Writer;
import java.nio.charset.Charset;
import java.util.Locale;
import java.util.concurrent.Callable;

import javax.annotation.processing.Processor;

/**
 * Interface to invoke Java&trade; programming language compilers from programs.
 * 
 * <p>
 * The compiler might generate diagnostics during compilation (for example,
 * error messages). If a diagnostic listener is provided, the diagnostics will
 * be supplied to the listener. If no listener is provided, the diagnostics will
 * be formatted in an unspecified format and written to the default output,
 * which is {@code System.err} unless otherwise specified. Even if a diagnostic
 * listener is supplied, some diagnostics might not fit in a {@code Diagnostic}
 * and will be written to the default output.
 * 
 * <p>
 * A compiler tool has an associated standard file manager, which is the file
 * manager that is native to the tool (or built-in). The standard file manager
 * can be obtained by calling {@linkplain #getStandardFileManager
 * getStandardFileManager}.
 * 
 * <p>
 * A compiler tool must function with any file manager as long as any additional
 * requirements as detailed in the methods below are met. If no file manager is
 * provided, the compiler tool will use a standard file manager such as the one
 * returned by {@linkplain #getStandardFileManager getStandardFileManager}.
 * 
 * <p>
 * An instance implementing this interface must conform to the Java Language
 * Specification and generate class files conforming to the Java Virtual Machine
 * specification. The versions of these specifications are defined in the
 * {@linkplain Tool} interface.
 * 
 * Additionally, an instance of this interface supporting
 * {@link javax.lang.model.SourceVersion#RELEASE_6 SourceVersion.RELEASE_6} or
 * higher must also support {@linkplain javax.annotation.processing annotation
 * processing}.
 * 
 * <p>
 * The compiler relies on two services: {@linkplain DiagnosticListener
 * diagnostic listener} and {@linkplain JavaFileManager file manager}. Although
 * most classes and interfaces in this package defines an API for compilers (and
 * tools in general) the interfaces {@linkplain DiagnosticListener},
 * {@linkplain JavaFileManager}, {@linkplain FileObject}, and
 * {@linkplain JavaFileObject} are not intended to be used in applications.
 * Instead these interfaces are intended to be implemented and used to provide
 * customized services for a compiler and thus defines an SPI for compilers.
 * 
 * <p>
 * There are a number of classes and interfaces in this package which are
 * designed to ease the implementation of the SPI to customize the behavior of a
 * compiler:
 * 
 * <dl>
 * <dt>{@link StandardJavaFileManager}</dt>
 * <dd>
 * 
 * Every compiler which implements this interface provides a standard file
 * manager for operating on regular {@linkplain java.io.File files}. The
 * StandardJavaFileManager interface defines additional methods for creating
 * file objects from regular files.
 * 
 * <p>
 * The standard file manager serves two purposes:
 * 
 * <ul>
 * <li>basic building block for customizing how a compiler reads and writes
 * files</li>
 * <li>sharing between multiple compilation tasks</li>
 * </ul>
 * 
 * <p>
 * Reusing a file manager can potentially reduce overhead of scanning the file
 * system and reading jar files. Although there might be no reduction in
 * overhead, a standard file manager must work with multiple sequential
 * compilations making the following example a recommended coding pattern:
 * 
 * <pre>
 *       Files[] files1 = ... ; // input for first compilation task
 *       Files[] files2 = ... ; // input for second compilation task
 * 
 *       JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
 *       StandardJavaFileManager fileManager = compiler.getStandardFileManager(null, null, null);
 * 
 *       {@code Iterable<? extends JavaFileObject>} compilationUnits1 =
 *           fileManager.getJavaFileObjectsFromFiles({@linkplain java.util.Arrays#asList Arrays.asList}(files1));
 *       compiler.getTask(null, fileManager, null, null, null, compilationUnits1).call();
 * 
 *       {@code Iterable<? extends JavaFileObject>} compilationUnits2 =
 *           fileManager.getJavaFileObjects(files2); // use alternative method
 *       // reuse the same file manager to allow caching of jar files
 *       compiler.getTask(null, fileManager, null, null, null, compilationUnits2).call();
 * 
 *       fileManager.close();
 * </pre>
 * 
 * </dd>
 * 
 * <dt>{@link DiagnosticCollector}</dt>
 * <dd>
 * Used to collect diagnostics in a list, for example:
 * 
 * <pre>
 *       {@code Iterable<? extends JavaFileObject>} compilationUnits = ...;
 *       JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
 *       {@code DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<JavaFileObject>();}
 *       StandardJavaFileManager fileManager = compiler.getStandardFileManager(diagnostics, null, null);
 *       compiler.getTask(null, fileManager, diagnostics, null, null, compilationUnits).call();
 * 
 *       for (Diagnostic diagnostic : diagnostics.getDiagnostics())
 *           System.out.format("Error on line %d in %d%n",
 *                             diagnostic.getLineNumber()
 *                             diagnostic.getSource().toUri());
 * 
 *       fileManager.close();
 * </pre>
 * 
 * </dd>
 * 
 * <dt>
 * {@link ForwardingJavaFileManager}, {@link ForwardingFileObject}, and
 * {@link ForwardingJavaFileObject}</dt>
 * <dd>
 * 
 * Subclassing is not available for overriding the behavior of a standard file
 * manager as it is created by calling a method on a compiler, not by invoking a
 * constructor. Instead forwarding (or delegation) should be used. These classes
 * makes it easy to forward most calls to a given file manager or file object
 * while allowing customizing behavior. For example, consider how to log all
 * calls to {@linkplain JavaFileManager#flush}:
 * 
 * <pre>
 *       final {@linkplain java.util.logging.Logger Logger} logger = ...;
 *       {@code Iterable<? extends JavaFileObject>} compilationUnits = ...;
 *       JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
 *       StandardJavaFileManager stdFileManager = compiler.getStandardFileManager(null, null, null);
 *       JavaFileManager fileManager = new ForwardingJavaFileManager(stdFileManager) {
 *           public void flush() {
 *               logger.entering(StandardJavaFileManager.class.getName(), "flush");
 *               super.flush();
 *               logger.exiting(StandardJavaFileManager.class.getName(), "flush");
 *           }
 *       };
 *       compiler.getTask(null, fileManager, null, null, null, compilationUnits).call();
 * </pre>
 * 
 * </dd>
 * 
 * <dt>{@link SimpleJavaFileObject}</dt>
 * <dd>
 * 
 * This class provides a basic file object implementation which can be used as
 * building block for creating file objects. For example, here is how to define
 * a file object which represent source code stored in a string:
 * 
 * <pre>
 *       /**
 *        * A file object used to represent source coming from a string.
 *        {@code *}/
 *       public class JavaSourceFromString extends SimpleJavaFileObject {
 *           /**
 *            * The source code of this "file".
 *            {@code *}/
 *           final String code;
 * 
 *           /**
 *            * Constructs a new JavaSourceFromString.
 *            * {@code @}param name the name of the compilation unit represented by this file object
 *            * {@code @}param code the source code for the compilation unit represented by this file object
 *            {@code *}/
 *           JavaSourceFromString(String name, String code) {
 *               super({@linkplain java.net.URI#create URI.create}("string:///" + name.replace('.','/') + Kind.SOURCE.extension),
 *                     Kind.SOURCE);
 *               this.code = code;
 *           }
 * 
 *           {@code @}Override
 *           public CharSequence getCharContent(boolean ignoreEncodingErrors) {
 *               return code;
 *           }
 *       }
 * </pre>
 * 
 * </dd>
 * </dl>
 * 
 * @author Peter von der Ah&eacute;
 * @author Jonathan Gibbons
 * @see DiagnosticListener
 * @see Diagnostic
 * @see JavaFileManager
 * @since 1.6
 */
public interface JavaCompiler extends Tool, OptionChecker {

	/**
	 * Creates a future for a compilation task with the given components and
	 * arguments. The compilation might not have completed as described in the
	 * CompilationTask interface.
	 * 
	 * <p>
	 * If a file manager is provided, it must be able to handle all locations
	 * defined in {@link StandardLocation}.
	 * 
	 * @param out
	 *            a Writer for additional output from the compiler; use
	 *            {@code System.err} if {@code null}
	 * @param fileManager
	 *            a file manager; if {@code null} use the compiler's standard
	 *            filemanager
	 * @param diagnosticListener
	 *            a diagnostic listener; if {@code null} use the compiler's
	 *            default method for reporting diagnostics
	 * @param options
	 *            compiler options, {@code null} means no options
	 * @param classes
	 *            class names (for annotation processing), {@code null} means no
	 *            class names
	 * @param compilationUnits
	 *            the compilation units to compile, {@code null} means no
	 *            compilation units
	 * @return an object representing the compilation
	 * @throws RuntimeException
	 *             if an unrecoverable error occurred in a user supplied
	 *             component. The {@linkplain Throwable#getCause() cause} will
	 *             be the error in user code.
	 * @throws IllegalArgumentException
	 *             if any of the given compilation units are of other kind than
	 *             {@linkplain JavaFileObject.Kind#SOURCE source}
	 */
	CompilationTask getTask(Writer out, JavaFileManager fileManager,
			DiagnosticListener<? super JavaFileObject> diagnosticListener,
			Iterable<String> options, Iterable<String> classes,
			Iterable<? extends JavaFileObject> compilationUnits);

	/**
	 * Gets a new instance of the standard file manager implementation for this
	 * tool. The file manager will use the given diagnostic listener for
	 * producing any non-fatal diagnostics. Fatal errors will be signalled with
	 * the appropriate exceptions.
	 * 
	 * <p>
	 * The standard file manager will be automatically reopened if it is
	 * accessed after calls to {@code flush} or {@code close}. The standard file
	 * manager must be usable with other tools.
	 * 
	 * @param diagnosticListener
	 *            a diagnostic listener for non-fatal diagnostics; if
	 *            {@code null} use the compiler's default method for reporting
	 *            diagnostics
	 * @param locale
	 *            the locale to apply when formatting diagnostics; {@code null}
	 *            means the {@linkplain Locale#getDefault() default locale}.
	 * @param charset
	 *            the character set used for decoding bytes; if {@code null} use
	 *            the platform default
	 * @return the standard file manager
	 */
	StandardJavaFileManager getStandardFileManager(
			DiagnosticListener<? super JavaFileObject> diagnosticListener,
			Locale locale, Charset charset);

	/**
	 * Interface representing a future for a compilation task. The compilation
	 * task has not yet started. To start the task, call the {@linkplain #call
	 * call} method.
	 * 
	 * <p>
	 * Before calling the call method, additional aspects of the task can be
	 * configured, for example, by calling the {@linkplain #setProcessors
	 * setProcessors} method.
	 */
	interface CompilationTask extends Callable<Boolean> {

		/**
		 * Sets processors (for annotation processing). This will bypass the
		 * normal discovery mechanism.
		 * 
		 * @param processors
		 *            processors (for annotation processing)
		 * @throws IllegalStateException
		 *             if the task has started
		 */
		void setProcessors(Iterable<? extends Processor> processors);

		/**
		 * Set the locale to be applied when formatting diagnostics and other
		 * localized data.
		 * 
		 * @param locale
		 *            the locale to apply; {@code null} means apply no locale
		 * @throws IllegalStateException
		 *             if the task has started
		 */
		void setLocale(Locale locale);

		/**
		 * Performs this compilation task. The compilation may only be performed
		 * once. Subsequent calls to this method throw IllegalStateException.
		 * 
		 * @return true if and only all the files compiled without errors; false
		 *         otherwise
		 * 
		 * @throws RuntimeException
		 *             if an unrecoverable error occurred in a user-supplied
		 *             component. The {@linkplain Throwable#getCause() cause}
		 *             will be the error in user code.
		 * @throws IllegalStateException
		 *             if called more than once
		 */
		Boolean call();
	}
}
